Add rootless Podman fixes, and others

improve container startup for rootless Podman, plus related refactors and tests. Key changes:

- Add/modify Audiobookshelf-related code and wiring (src/lib/services/audiobookshelf/api.ts, library service refs) and update documentation TABLEOFCONTENTS to reference ABS implementation.
- Detect user namespace in docker/unified app-start.sh and redis-start.sh and skip gosu when running in rootless Podman to preserve UID mapping; improve startup logging and verification.
- Add utility/service files (auth-token-cache.service.ts, credential-migration.service.ts, cleanup-helpers.ts) and corresponding tests; update chapter-merger and metadata-tagger utilities/tests.
- Update many admin/auth API routes and tests to reflect changes in settings and integrations.
- Remove large AI agent and Audiobookshelf implementation guide docs (AGENTS.md and the implementation guide) and add README note about AI-assisted workflow.

These changes enable Audiobookshelf backend mode, improve compatibility with rootless container runtimes, and include cleanup/refactor work and unit tests.

src/lib/utils/chapter-merger.ts

@@ -676,9 +676,14 @@ export async function mergeChapters(
     args.push('-avoid_negative_ts', 'make_zero'); // Handle negative timestamps
     args.push('-max_muxing_queue_size', '9999'); // Prevent buffer overflow on long files
 
-    // Add book metadata
+    // Add book metadata (escape for double-quoted shell context)
+    // Single quotes do NOT need escaping inside double quotes - they are literal
     const escapeMetadata = (val: string): string =>
-      val.replace(/"/g, '\\"').replace(/'/g, "\\'");
+      val
+        .replace(/\\/g, '\\\\') // Backslashes first
+        .replace(/"/g, '\\"') // Double quotes
+        .replace(/`/g, '\\`') // Backticks
+        .replace(/\$/g, '\\$'); // Dollar signs
 
     args.push('-metadata', `title="${escapeMetadata(options.title)}"`);
     args.push('-metadata', `album="${escapeMetadata(options.title)}"`);